208 NANOMIA CARA. 



polyp ; as has already been shown by Sars in Agalmopsis, the sexes are 

 distinct, so that we have whole communities, the sexual Medusae of 

 which are either males or females. There is no great differeiice be- 

 tween the appearance of the male and female Medusae ; they do not 

 (as is the case in Agalmopsis, according to Sars) separate from the com- 

 munity, and lead an independent existence ; they wither on the stem, 

 after having discharged their contents. The Medusae form bunches, 

 the single Medusae of which are directly attached to the main axis ; 

 they are somewhat pointed in outline, with four tolerably well defined 

 Fiff. 346. chymiferous tubes, resembling quite closely the sessile Me- 



Idusae of such Tubularians as Tubularia Couthouyi. 

 From the observations of Gegenbaur, there can be no doubt 

 that many of the Siphonophores are, like Nanomia, developed 

 directly from the egg, and that the embryo which comes from 

 the egg is one which is identical with those found floating 

 about in such immense numbers during the early part of 

 June, and which are figured in Fig. 346, consisting of a single closed 

 polyp and of an oil-float, separated by a partition, as in the adult (Fig. 

 331) ; this simple polyp is to be the axis of the future community. 

 But these young Nanomiae (Fig. 346) do not all arise from eggs, and 

 pass directly into an embryo like Fig. 346 ; we have a second kind 

 of development, that of budding. In Fig. 338 there is represented on 

 the top an appendage resembling somewhat a polyp without an open- 

 ing, having neither tentacle nor protecting scale. A bubble of oil is 

 collecting at the proximal extremity ; as this bubble increases in size, 

 the neck which connects the polyp with the main axis gradually 

 becomes narrower and narrower, until the connection is finally cut, 

 and we have a bud resembling in every respect Fig. 346, which has 

 separated from the main community. By keeping in confinement. 

 Fig. 347. entirely isolated, an adult Nanomia having many of these 



buds along the main axis, I have found after a few days 

 a large number of these buds liberated, which had as- 

 sumed the shape and structure of Fig. 346, and had 

 grown to be similar in every respect to the embryos I 

 was fishing from the sea at the same time. From this 

 I should infer that we have two broods of adults, those 

 which are found in the fall, and which lay eggs in Octo- 

 ber and November, and those which are probably formed by budding 

 from the older ones during the summer and winter ; the embryos found 

 in early summer may have come from the eggs of either of these. 



The young embryos (Fig. 346) readily keep alive in confinement, 

 and it is a comparatively easy thing to trace the successive stages of a 



Fig. 346. Youngest Nanomia found swimming on surface. 

 Fig. 347. Somewhat more advanced. 



